A scroll fluid machine is provided with a pair of a stationary scroll and an orbiting scroll. The scrolls each include an end plate with a spiral wrap disposed in an upright manner thereon. The pair of the stationary scroll and the orbiting scroll are engaged by opposing their spiral wraps with a 180 degree phase difference, thus forming a sealed chamber between the scrolls. As a result, the scroll fluid machine is configured to supply and discharge fluid. In such a scroll fluid machine, a scroll compressor for example, a two-dimensional compression structure is generally adopted in which the wrap heights of the spiral wraps of the stationary scroll and the orbiting scroll are set to be constant over the entire length in the spiral direction, a compression chamber is caused to move from the outer circumferential side to the inner circumferential side while gradually having its capacity reduced, and the fluid is compressed in the circumferential direction of the spiral wraps.
Meanwhile, in order to improve efficiency of the scroll compressor and to achieve downsizing and weight-reduction thereof, a three-dimensional compression-type scroll compressor has been proposed. Such a three-dimensional compression-type scroll compressor has a structure in which a step part is provided at a predetermined position, along the spiral direction, on each of the tooth crest and the tooth base of the spiral wraps of the stationary scroll and the orbiting scroll, such that the step part forms a boundary at which the wrap height of the spiral wraps transitions from higher on the outer circumferential side to lower on the inner circumferential side. By causing the height of the compression chamber in the axial direction to be higher on the outer circumferential side of the spiral wraps than on the inner circumferential side thereof, the fluid is compressed both in the circumferential direction and the height direction of the spiral wraps.
In such a scroll fluid machine, the spiral wraps of the stationary scroll and the orbiting scroll are normally machined by an end mill. However, due to machining problems (mainly due to factors such as changes in a pressing force of the tool and wear of the tooth tip), a taper-shaped protrusion (hereinafter also referred to as a reduced machining-accuracy area) is susceptible to being formed at a base portion of the spiral wrap. As a result, a gap is generated between the spiral wraps due to a contact failure, this gap becoming a cause of gas leaks. As countermeasures against the problem, as disclosed in Patent Documents 1 and 2, for example, a scroll fluid machine is known in which tapered chamfering and the like is carried out on a tooth tip section of the spiral wrap of a partner scroll.
Further, in Patent Documents 3 and 4, and the like, a scroll fluid machine is disclosed in which, in order to prevent an increase in wear and stress caused by the orbiting scroll interfering with the partner scroll as a result of being tilted or becoming thermally deformed when driven to orbit, the front-side surface or the rear-side surface of the tooth tip section of each of the spiral wraps is provided with a relief portion, a thinned section and the like in the direction in which the wrap thickness decreases, thereby inhibiting the interference between the orbiting scroll and the partner scroll.